1. Field of the Invention
The present invention relates to the field of analog attenuators.
2. Prior Art
Variable analog attenuators are commonly used in applications which require signal level control, such as, by way of example, in radio frequency (RF) automatic gain control (AGC) circuits. Typically discrete PIN diodes are used for this purpose. A PIN diode differs from an ordinary PN diode in that there is an intrinsic semiconductor region (I) between the P and N doped regions of the diode. When a forward bias is applied to the diode, a large number of electrons and holes are created in the intrinsic region, allowing forward conduction. If the bias is suddenly removed, these charge carriers will not immediately recombine, and thus will not immediately stop the conduction current. Thus PIN diodes will conduct high frequency signals superimposed on a bias current without much distortion, even for large signals that would cause a momentary reversal of the PIN diode current. However the present invention performs the desired function, but being part of an integrated circuit, is smaller, less expensive, has less power consumption and provides constant attenuation versus control voltage slope when compared to conventional discrete PIN diode based analog attenuators.